The 66/68RFE has NOT been around for 18 years.
If you are counting the 4 and 5-speed version since they share the last RFE designation then I can say that the 8HP design has been around since the early 90s with the inception of the 5HP since they share the same base design. Saying either is just ludicrous.
The torque limitations on the 68RFE is a major reason why the Cummins has such a restrictive torque management versus the other diesel's. But what do I know, I only worked for Cummins and been in the heavy and medium duty industry for over two decades.[/QUOTE
The 45RFE that came out in I believe the 99 Grand Cherokee 4.7.
Was always capable of being a 6 speed, all the planetaries were there. Same basic design, Beefed up, larger case, More clutch packs,heavier converter, larger components in the 66/68 RFE. So not ludicrous. How many have you had apart?
I can't comment on the 5HP because I know nothing about it and have never had one apart
What does working for Cummins have to do with anything?
Sorry your getting but hurt. Because someone disagrees with you.